The present invention relates to a cylinder head gasket which is held between engine members and seals therebetween, specifically, a cylinder head gasket which can control the deformation of the engine members by equalizing a seal surface pressure, and a method of making a cylinder head gasket.
The cylinder head gasket of an engine is tightened by bolts in a state of being sandwiched between two members, such as a cylinder head and a cylinder block (cylinder body), of the engine of an automobile, and has a role for sealing fluid such as combustion gas, oil, coolant water and the like.
Comparing to conventional engines, recent engines have a tendency to change material from cast iron to aluminum alloy due to downsizing and reducing weight, and increase the pressure of combustion gas due to a higher power engine. Therefore, in the case wherein a cylinder is unevenly placed from the center of the width direction of the engine, the distribution of the surface pressure acting on the cylinder head through beads becomes uneven, and the cylinder head cannot be evenly pressed, so that the cylinder head may be deformed.
As a foregoing metal gasket, a cylinder head gasket, which is a metal cylinder head gasket for a multi-cylinder internal-combustion engine wherein the cylinder is arranged toward one side relative to the width direction, was proposed (for example, see the Japanese Patent Publication No. H10-19130). This cylinder head gasket has looped stepwise beads whose cross-sectional shape is stepwise along the peripheral border of the gasket in at least one sheet of gasket plates. In the cylinder head gasket, the strength of the beads located at a small area of the gasket when dividing the gasket by a line connecting the centers of cylinder bores, is strong, and the strength of the beads located at a large area of the gasket when dividing the gasket by the line connecting the centers of the cylinder bores, is weak.
In the metal laminate gasket, the seal surface pressure can be even throughout the gasket, and the sealing performance of the beads provided around water holes, oil holes and the like can be improved. However, if the looped stepwise beads are arranged around the gasket, a comparatively long bead is formed as compared to the case wherein the beads are arranged at a peripheral border portion of the cylinder bore, so that a high seal surface pressure cannot be retained well in the peripheral border portion of a sealing bore.
On the other hand, in order to prevent the deformation of a longitudinal direction of the cylinder head, a metal gasket with temperature-resistant, incompressible, and non-deforming projections, which are provided only on both ends of the longitudinal direction of the gasket, was proposed. Also, in order to prevent the deformation in the width direction of the cylinder head, a metal cylinder head gasket with anti-bending projections, each being provided between each of two end edges in the width direction and each through-bore, was proposed (for example, see Japanese Patent Publications No. H9-292027 and No. 2003-42295). The anti-bending projection has a large rigidity relative to a load in a compressive direction, and acts substantially as a rigid body relative to a locking force of each bolt.
In the above-mentioned cylinder head gaskets, the shape, length and the like of the anti-bending projection are not described. Also, the anti-bending projection has a role for preventing a seal projection (beads or the like) from being compressed excessively, and functions as the rigid body from a certain height. Therefore, in the case wherein the gasket is pressed from the certain height, the seal surface pressure of the seal projection does not increase.
The present invention has made in order to solve the problems described above, and an object of the present invention is to provide a cylinder head gasket held between two engine members for sealing therebetween, which can easily be designed as a means for preventing the deformation of the cylinder head based on a sealing means such as a bead and the like, and also can retain a high seal surface pressure.
Another object of the invention is to provide a method of designing the cylinder head gasket with the above structure.
Further objects and advantages of the invention will be apparent from the following description of the invention.